Fuel feed system



Jan. 21, 1941. n. SAMIRAN FUEL FEED SYSTEM v I /N /V7'0R DAV/0 SAM/RAN Filed July 26, 1938 Patented Jan. .21, 1941 UNITED STATES PATENT OFFICE 11 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a system for control ling power delivered from a source to a delivery point, and more particularly to an hydraulic system for controlling the transmission of power, and is adapted for use in connection with the supplying of liquid fuel or other fluid from a source of supply to a delivery point, and is especially useful in connection with the supply of gasoline from a supply tank to an internal combustion engine remote from said tank,

, It has been found that where, in the case of aircraft, the fuel'is stored in a tank remote from jacent to the source of fuel supply, the reciprocating air or reciprocating compression pump serving to supply driving fluid under pressure to the fluid motor driven pump, and the fluid motor driven pump serving to draw fuel from the'source of fuel supply and forcing, under pressure, the fuel so drawn by the fluid motor driven pump to the point of delivery, provision being madefor controlling the pressure and amount of the fluid supplied to the fluid motor driven pump by the pressure or amount of liquid fuel delivered by the fluid motor driven'pump to the point of delivery, decreasing the pressure and amount of fluid supplied to the fluid motor driven pump with increase above normal in the pressure or amount of the fuel at the point of delivery, and increasing the pressure and amount of fluid supplied to the fluid motor driven pump on decrease below normal in the pressure or amount of the fuel at the point of delivery. v

A further conventional method of supplying fuel from a source of supply to an engine at a given pressure is that of employing a positive displacement fuel pump, driven directly by the'engine, the fuel supply pressure being controlled by shunting the fuel pump by the use of a pressure relief valve. These known systems, however, have certain disadvantages. A reciprocating compression pump in the first mentioned system has the disadvantage that it depends for its output upon the atmospheric pressure which varies with change in altitude so that a system of this character designed for high altitude operation, where the atmosphere is less dense or rarefied, would be extremely oversize for low altitude operation.

The expansion of a compressible fluid as it passes .through the driving motor results in a lowering of its temperature and in the case of air would cause a condensation and freezing of the moisture in the air. In such a system, therefore, satisfactory operation makes it imperative that the air be warm. This can only be accomplished by applying heat from an external source.

Sudden changes in the demand of the fuel supply at the point of delivery require instantaneous response of the fuel supply pump so that where the fluid motor driven pump is driven by a compressible fluid under pressure that is built up in the system, the change insupply of fuel to the point of delivery can not be instantaneous because of the compressibility of the fluid and the consequent time lag in building up the fluid pressure by'the compression pump and delivering the same to the fluid driven motor.

A system of this character in which reciprocating compressors, motors, or pumps are utilized in the fuel path have the further disadvantage of producing, by reason of the presence of valves, vapor lock which is brought about by the fuel undergoing a drop in pressure as it passes through the valves and particularly so through the suction valve where a partial vacuum is created inside the pump on the suction stroke. At high altitudes, where the pressure at the inlet of the valve is already near the boiling pressure of the fuel, slight reductions in pressure in pumping the fuel through the valve will cause almost instantaneous vaporization of the more volatile fractions of the fuel and will result in vapor lock condition, rendering such a system of no practical utility in aircraft.

In the second-mentioned system, the excess fuel being forced through the relief valve represents wasted work and horsepower. When the inlet of the fluid pump is subjected to pressures and temperatures near the pressure and tem- 5 perature at which the fluid changes from (gaseous to liquid or vice versa) the drop in pressure encountered by the excess liquid when passing through the relief valve causes vapor to form, which vapor when returned to the pump suction vapor locks the pump until pumping ceases. To illustrate, this drop in pressure in a present-day airplane fuel system operating at 40,000 feet altitude is from approximately 18% pounds per square inch absolute carburetor pressure to approximately 2 pounds per square inch absolute atmospheric pressure. The rellei volve couurols the pressiue at the point oi iiom the pump (provided it is mounted on the pump) and not at the point of consumption, ihereziore when the point of consumption is remote doom the pump and use didereuce in elevation (static head) of the two changes (as in airplane maneuvering) the pressure at the point of consumption changes from the discharge pressiu'e' of the fluid pump in accordance with this change in static head.

My invention, ther fore, has for one of its objects to provide, in on hydraulic transmission system for supplying fuel from a. source of supply to a. point of delivery, on automatically replenishlug partially closed hydraulic power transmission circuit, the power transmission of which is mode variable as a. function of the pressure of the fluid supplied at the point of delivery.

A further object of this invention is to make provision for supplying the transmission circuit with loci from the source oi fuel supply, as a. transmission medium, and for maintaining sold circuit substantially completely filled, at all times, regardless of the fluid flow tmnsmlssiou speed or variation in the pressure of the fuel supplied at the point oi delivery.

A further object of this invention is to com meet, in a. system of this character, the pressure transmission circuit, in parallel, with the fuel delivery line and to provide means whereby the transmission circuit is supplied with o. transmission fluid from the source of fuel supply and is maintained substantially completely filled at all times, with transnussion fluid regardless of the fluid flow transmission speed or variation in the pressure of the fluid supplied at the point of delivery.

A still further object of this invention is to provide, in a. system of this character, a. fluid pressure transmission circuit having means for generating fluid pressure to drive s. duel pump o nd for supplying and replenishing the transmission medium from the source to the transmission line in accordance with a. pressure difference between the suctions of the power generating means and the fuel pump and independently of the rate of supply of fuel to the point of delivery.

Another object. of this invention is to provide, in a. system of this character, means communicatively connected between the in-put side of the fluid pressure generator and the source of supply for shunting the pressure transmission mediumfrom the; transmission circuit to the source.

Another object of this invention is to provide,

in a'syste-m of this character, utilizing part of the engine fuel as a transmission medium, means for bleeding air from the fuel in the transmission circuit to the fuel pump. Y

A further object of this invention is to provide, in a. system of this character, means for maintaining at all times a. substantially constant differential between the carburetor air inlet pressure and the fuel pressure at the point of delivery regardless of pressure variations of the ambient atmosphere.

A further object of this invention is to provide,

' in a system of this character, an air or-vapor eliminotor for lay-passing fuel vapors from the fuel being delivered by the fuel pump to the carburetor.

Other and further objectsof this invention will appear from a. more detailed descriptiono! this invention taken in connection with the' drawing deco es which iorms a. part of the specificstion, and in which:

Figure l is a. schematic view of .2. fuel feedin sys'ioem embodying my invention.

Figure 2 is an enlarged detail view.

Figure 3 e. fractional sectional view showing the connection. oi the system with the intake of ihe mouiiold.

Figure 4 is an enlarged sectional detail view of the elimlnaior embodied in the system.

Referring to the drawing, Figure 1 illustrates diagrammatically o system embodying this invention. in the embodiment shown in the drawing, which illustrates the means for cal Tying out this invention as applied to the supply of fuel any ores elected one of the sources of fuel supply A, B, C in the main and reseive tanks ill and ill to an internal combustion engine M, the fuel is delivei'ed from any preselected'one of these sources through tubes as, ill and 20 re spectively to a. selector valve 22, a. strainer and into a. reserve expansion chamber or sump 25 throimh a. conduit 26 from which it is dellve ed to a carburetor 2? through c. fluid driven positive displacement metering pump of any well lmown make and through an air or vapor elimimotor 36!, the air or vapor eliminator being commumcotively connected at its upper end with the tank id by means of s. tube 32 to permit the gas vapor to return to the tank.

The positive displacement pump 28 is preferably of the rotary type and is driven by an bydrsulic motor 34 which is preferably oi the reciprocating type, as described in Patent No. 2,083,566, issued June 5, 1931- The motive or operating liquid, which as illustrated herein is part of the fuel supply, is supplied to the hydraulic motor 34 by means of on hydraulic genorator so, which, preferably is or the well known gear pump type. The generator 35 is driven by means of suitable gearing and an adaptor drive or extension drive shaft assembly 38 at some definite speed ratio of the crankshaft R. P. M. The adaptor drive 38 sets the hydraulic generator 36 away from the engine so that the generator clears, adjacent units such as magnetos, oil pumps, etc. The generator 36 is connected at its input side with the output side of the hydraulic motor 34 through a conduit 40 and branch conduit 42, the supply of fluid from the output side of the generator to the input side of the hydraulic motor being transmitted through conduits M and 46 and through a. fuel pressure responsive regulator or control unit 48 therebetween. The regulator =18 is shunted to the input side of the. generator through a. conduit 59. The input side of the generator 36 is also communicativcly connected to the expansion chamber 25 through a spring loaded check valve 52 in a, branch line 54-56; It will thus be seen that when starting or before the lines are filled with liquid, hydraulic pressure generator 38 draws fuel from expansion chamber 28 through conduit 56, check valve 52, conduit 54 and conduit 40. On the pressure side or the generator the liquid flows through conduit H, the fuel pfessure control unit 48 and conduit 46 to the pressure side of the hydraulic motor 34. After the conduits are filled with liquid the flow is from' the discharge side of hydraulic motor 34, through conduits 42 and 40 to the inlet or suction side of the pressure generator, but flow on the pressure side remains unaltered and check valve 52 now remains closed.

The fuel pressure at the point; of consumption, 1. e. at the carburetor, is also regulated by control unit 48. This control unit consists of a spring loaded valve 58 and a metallic bellows 68, the bellows being sealed in anair tight housing 62. The sealed inner chamber 64 of the bellows housing is in direct communication with the fuel pressure line 66, branch line 58 being used for this purpose. The bellows has an area several times larger than that of the control valve and is fixed in the housing at its lower end, the upper end being free to move downward under the influence of fuel pressure. Through conduit 18 the inner chamber 12 of the bellows is in direct communication with the intake manifold I4, the pressure therein being preferably determined by a super-* charger 15 f any well known construction. The control valve has an upper stem 16 and a lower stem '18, both being guided in the housing, with the upper one attached to the movable end of the aforementioned bellows.- The pressure control valve is loaded with a helical coil spring 88 that seats on the end of a screw 82, the latter being threaded into the housing and locked securely with a locknut 84, as shown. In the hydraulic drive system here disclosed, hydraulic motor 34 and fuel pump 28 are integrally connected and operate in unison, hence by utilizing the fuel pressure to control the motor, the pump speed is varied accordingly. It will therefore be obvious that the fuel pressure can be controlled or held constant by varying the speed of the fuel pump through the control of the hydraulic motor to suit the requirements of the engine. unit 48 operates, as already noted, to vary the speed of the hydraulic motor and the fuel pump by by-passing some of the liquid from the pressure side of hydraulic generator 36 to the suction side. It will be noted that liquid from the pressure side of generator 36 flows through line 44 to the lower chamber 45 of control unit 48, and that this chamber remains closed by the control valve 58 so long as the latter is seated in the housing 86. With the control valve closed, liquid flows from the lower chamber 45 of 1mit 48 through conduit 46 to the pressure side of hydraulic motor 34. The spring load on the control valve 58 is set by means of the screw adjustment provided so that the valve will open at some predetermined orjdesired value of the fuel pressure. When fuel entering the chamber 64 through line 68 causes the bellows to exert a force on the control valve which is slightly greater than that of the combined load caused by the spring, the hydraulic pressure acting on the under side of the valve 58 and the manifold pressure being applied through line I0 to the inside 12 of the bellows, the control valve will open. Opening of the control valve 58 permits some of the hydraulic liquid from the lower pressure chamber 45 to enter the central chamber 88 where it flows out through branch conduit 58 to the main suction line 40 of hydraulic generator 38. Reducing, in this manner, the pressure and volume of the operating liquid to the pressure side of the hynormal engine operation there is always an ex-' cess of pressure available for control purposes.

In order to prevent the withdrawal of fuel from the transmission circuit by the fuel pump when any of the tanks is emptied, the sump or liquid trap 25, best shown in Figure 2, is providedin Control the conduit between the strainer 24 and the fuel pump 28 so that there is always liquid therein, and the conduit 56 in communication, with the check valve 52. is at all times immersed in this liquid. With this arrangement it is possible to maintain an operating liquid in the transmission circuit after the-fuel tank is emptied.

Provision is made for eliminating air or vapors from the transmission circuit as well as to prevent excessive pressures being built up in the hydraulic lines. For this purpose a restricted passage such as conduit 98 connects the hydraulic motor discharge conduit 42 to the sump at the suction side of the fuel pump through'a spring loaded check valve 92 and conduit 94. Preferably the conduit 80 is of such small cross sectional area that the friction of liquid therein prevents any'substantial volume of liquid from being transferred therethrough. However this passage does not offer such a high resistance to flow of airtherethrough and hence readily permits the transfer of air to the suction side of the pump. The spring load on the check valve is adjustable and as illustrated is preferably such that under normal operating conditions of the fuel supply system the check valve 92 slightly opens permitting seepage or bleeding of fluid from the transmission circuit to. the input side of the fuel pump: However, when the suction effect of the fuel pump on this check valve ceases, when the supply tank is empty, the valve opening will remain closed, thus providing a closed circuit for the pressure fluid in the power transmission circuit.

For operation of the hydraulic drive fuel system when the engine is not running, starting, etc., or in case of emergency, failure of engine driven pressure generator 36 to operate, or for other reasons, hand pump 96 can be used. A new arrangement of the hand pump is'shown whereby it is used to drive directly the hydraulic motor 34 and indirectly, through the integral. construction of rotating elements, the positive displacement metering fuel pump 28. With the engine at rest, operating hand pump 96, being communicatively connected with the conduit 40 through conduit 98, first draws fuel from the sump 25 and circulates the same in the same manner as the generator 36. On thepressure side of the pump, the fuel flows through conduit I00 to its junction with 44 to the pressure chamber 45 of control unit 48, then on through line 46 to the pressure side of hydraulic motor 34. A few strokes of the hand pump at the beginning suifice to fill the system with liquid, after which check valve- 52 remains closed and the fuel pressure builds up to a value limited by the adjustment of control unit 48. If the hand pump is operated at a speed greater than that necessary to supply the quantity of fuel required at the desired pressure, the control valve 58 of the unit-48 opens and bypasses liquid from the pressure chamber 45 to the central chamber 88 and through conduit 58 to the suction side of the pump. Hence for hand pump operation, control unit 48 functions just described by the speed of operation of the pump 28, which in turn is controlled by the regulation of the pressure transmission circuit as a function of the pressure of the fuel at the point of delivery. As heretofore briefly described, an air eliminator (best shown in Figure 4) is provided foregoing description, and all changes which for eliminating any airor vapor in the y tem.

prior to its admission tothe carburetor. The air eliminator 30, which consists essentially of a casing I02 and a float controlled valve unit I, is communicatively connected at its inlet I08 with the output side of the pump 28 and through outlets I08 and H0 with the carburetor 21 and tank It! respectively. It will be seen that, as the fuel is delivered into this air eliminator by the fuel pump 28 from the sump 25, the fuel is deflected by a deflector H2, causing the same to move upwardly prior to its emission therefrom through outlet I08. since the float controlled valve u'nit I06 is so constructed as to be buoyantly supported by the fuel, it will normally close the valve opening H4 until such time when the air and vapor pressure in the chamber 6 is such as to lower the level of the fuel in the. chamber to a point where the valve opening is no longer closed,

whence the air and vapor will be permitted to escape through the conduit 32 and into the tank Ill. I

This embodiment of my invention is to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended,claims rather than by the come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What I claim and desire to secure by United States Letters Patent is:

1. In a fuel feed supply system, a source of fuel supply, fluid driven pump means for supplying fuel from said source under pressure to a. point of delivery, and a fluid pressure transmission circuit for regulating the supplying of an operating fluid pressure to'said pump means as a function of the fuel pressure at the point of delivery, said circuit including amotor for operating said pump means, and a fluid pressure generator connected at its output with the input of said motor and being commonly communicatively connected at its input with the output of said motor and to said source at the input side of said pump means.

2. In a fuel feed system, a source of fuel supply; a pumpfor supplying fuel from said source under pressure to a point of delivery, and a fluid pressure transmission circuit in communication with said source of supply at the input aid: :1 said pump and adapted for operating said pump in accordance with a predetermined fuel pressure at the point of delivery, said circuit comprising a fluid pressure generator, a fluid motor for actuating said pump and means between said generator and said motor responsive tochanges in the pressure at the point of delivery for controlling the supply of fluid pressure to said motor.

3. In a fuel feed supply system, a source of fuel supply, fluid driven pump means for supplying fuel from said source under pressure to a point of delivery, and a fluid pressure transmission circuit for regulating the supplying of an operating fluid pressure to said pump means as a. function of the fuel pressure at the point of daily ery, said circuit including a motor for operating said pump means, a fluid pressure generator connected at its output with the input of said motor and being commonly communicatively connected at its input with the output of said motor and to said source at the input side of said pump means and valve means in the line between the output of said motor and the source of supply to prevent return of fluid from said line to said source.

4. In a fuel feed system, a source of fuel supply, a pump for supplying fuel from said source under pressure to a point of delivery, and a fluid pressure transmission circuit in communication with said source of supply and adapted for operating said pump in accordancewith a predetermined fuel pressure at the point of delivery, said circuit comprising a fluid pressure generator, a fluid motor for actuating said pump and means between said generator and said motor responsive to changes in the pressure at the point of delivery for controlling the supply of fluid pressure to said motor, and valve means in the line between the output of said motor and the source of supply to prevent return of fluid from said line to said source.

5. In a fuel feed supply system, a source of fuel supply, fluid driven pump means for'supplying fuel from said source under pressure to a point of delivery, and a fluidpressure transmission circuit for regulating the supplying of an operating fluid pressure to said pump means as. a function of the fuel pressure at the point of delivery, said circuit including a. motor for operating said pump means, and a fluid pressure generator connected at its output with the input of said motor and being commonly eommunicatively connected at its input with the output of said motor and to said source at the input side of said pump means and means responsive to changes in the pressure of said fuel at said point of delivery for controlling the operating fluid in the said transmission circuit to maintain said pressure at the point of delivery substantially constant at a predetermined value.

6. In a. fuel feed supply system, a source of fuel supply, fluid driven pump means for supplying fuel from said source under pressure to a point of delivery, and a fluid pressure transmission circuit for regulating the supplying of an operating fluid pressure to said pump means as a function of the fuel pressure at the point of delivery, said circuit including a motor for operating said pump means, and a fluid pressure generator connected atits output with the input of said motor and being commonly communicatively connected at its input with the output of said motor and to said source at the input side of said pump means and means responsive to changes in the pressure of v said fuel at said point of delivery for controlling the operating fluid in the said transmission circuit to maintain said pressure pressure at the point of delivery substantially constant at a predetermined value and means connected between the output side of said motor and the input side of said pump for vent- 'ating said pump means, and a flui 'pressure generator connected at its output th the input of said motor and being commonl ,communi'catively connected at its input with the'output of said mctorand to said source at the input side of said pump means, valve means in the line between the output of said motor and the source of supply to prevent return of fluid from said line -to said source and means for venting said circuit of supply and adapted for operating said pump ner as to obtain a pressure diflerence between the in accordance with a predetermined fuel pressure at the point of delivery, said circuit comprising a fluid pressure generator, a fluid motor for actuating said pump, means between said generator and said motor responsive to changes in the pressure at the point of delivery for controlling the supply of fluid pressure to said motor, valve means in the line between the output of said motor and the source of supply to prevent return of fluid from said line to said source, means for venting said circuit to the input side of said pump, and a chamber communicatively connected with said pump, said source, said valve means, and said vent means in such a manner as to provide at all times a supply of operating fuel for replenishing said circuit.

9. Means for maintaining a substantially constant pressure difference between the fuel pressure and the inlet air pressure of the carburetor of an internal combustion engine comprising a fluid pressure transmission circuit for regulating fuel pressure and the inlet air pressure substantially corresponding to said predetermined load.

10. In a fuel feed supply system, a source of fuel supply, fluid driven pump means for'supplying fuel from said source under pressure to a point of delivery, and a fluid pressure transmission circuit for regulating the supplying of an operating fluid pressure to said pump means as a function of the fuel pressure at the point of delivery, said circuit including a motor for oper ating said pump means, and a fluid pressure generator connected at its output with the input of said motor and being commonly communicatively connected at its input with the output of said motor and to said source at the input side of said pump means and means responsive to changes in the pressure of said fuel at said point of delivery for controlling the operating fluid in the said transmission circuit to maintain said pressure at the point of delivery substantially constant at a predetermined value and a venting conduit connected between the input side of said pump and at a point of pressure between the output side of said motor and the input side of said generator that is relatively greater than the pressure at the input side of said pump.

11. In a fuel feed supply system, a fuel containing chamber, fluid driven pump means for supplying fuel from said chamber under pressure to a point of delivery and a fluid pressure transmission circuit for regulating the supply of an operating fluid pressure to said pump means as a function of the fuel pressure at the point of delivery, said circuit inciuding a motor for operating said pump means, a fluid pressure generator connected at its output with the input of said motor and being commonly communicatively connected at its input with the output of said motor and to said chamber ,at the input side of said pump means and at a level in said chamber below the point of connection between said pump and said chamber and valve,means in the line between the output of said motor and the chamber to Prevent return of fluid from said line to said chamber.

DAVID SAMIRAN. 

